1Kernel driver ds1621
2====================
3 4Supported chips:
5 * Dallas Semiconductor DS1621
6 Prefix: 'ds1621'
7 Addresses scanned: I2C 0x48 - 0x4f
8 Datasheet: Publicly available at the Dallas Semiconductor website
9http://www.dalsemi.com/ 10 * Dallas Semiconductor DS1625
11 Prefix: 'ds1621'
12 Addresses scanned: I2C 0x48 - 0x4f
13 Datasheet: Publicly available at the Dallas Semiconductor website
14http://www.dalsemi.com/ 15 16Authors:
17 Christian W. Zuckschwerdt <zany@triq.net>
18 valuable contributions by Jan M. Sendler <sendler@sendler.de>
19 ported to 2.6 by Aurelien Jarno <aurelien@aurel32.net>
20 with the help of Jean Delvare <khali@linux-fr.org>
21 22Module Parameters
23------------------
24 25* polarity int
26 Output's polarity: 0 = active high, 1 = active low
27 28Description
29-----------
30 31The DS1621 is a (one instance) digital thermometer and thermostat. It has
32both high and low temperature limits which can be user defined (i.e.
33programmed into non-volatile on-chip registers). Temperature range is -55
34degree Celsius to +125 in 0.5 increments. You may convert this into a
35Fahrenheit range of -67 to +257 degrees with 0.9 steps. If polarity
36parameter is not provided, original value is used.
37 38As for the thermostat, behavior can also be programmed using the polarity
39toggle. On the one hand ("heater"), the thermostat output of the chip,
40Tout, will trigger when the low limit temperature is met or underrun and
41stays high until the high limit is met or exceeded. On the other hand
42("cooler"), vice versa. That way "heater" equals "active low", whereas
43"conditioner" equals "active high". Please note that the DS1621 data sheet
44is somewhat misleading in this point since setting the polarity bit does
45not simply invert Tout.
46 47A second thing is that, during extensive testing, Tout showed a tolerance
48of up to +/- 0.5 degrees even when compared against precise temperature
49readings. Be sure to have a high vs. low temperature limit gap of al least
501.0 degree Celsius to avoid Tout "bouncing", though!
51 52The alarm bits are set when the high or low limits are met or exceeded and
53are reset by the module as soon as the respective temperature ranges are
54left.
55 56The alarm registers are in no way suitable to find out about the actual
57status of Tout. They will only tell you about its history, whether or not
58any of the limits have ever been met or exceeded since last power-up or
59reset. Be aware: When testing, it showed that the status of Tout can change
60with neither of the alarms set.
61 62Temperature conversion of the DS1621 takes up to 1000ms; internal access to
63non-volatile registers may last for 10ms or below.
64